Rectification method for separating and purifying 1, 3-propylene glycol based on fermentation of renewable biomass

Abstract

The invention provides a rectification method for separating and purifying 1, 3-propylene glycol based on fermentation of renewable biomass, the rectification method adopts a crude distillation tower to distill a concentrated solution obtained by multi-effect evaporation, creatively uses a scraper evaporator as a reboiler of the crude distillation tower, can effectively prevent a high-viscosity salt-containing material from blocking the reboiler of the crude distillation tower, and improves the yield of 1, 3-propylene glycol. The combination of the crude distillation tower and the scraper evaporator realizes the separation and purification effects of two processes of crude distillation and rectification by using one process, simplifies the process flow, reduces the equipment investment, and reduces the energy consumption; moreover, according to the rectification method, simultaneous separation of 2, 3-butanediol and 1, 3-propylene glycol can be realized by adopting the second rectification tower, so that the process is simplified, the energy consumption is reduced, 1, 3-propylene glycol with the purity greater than or equal to 99.9 wt% can be prepared, and the quality requirement of a polymer-grade product is completely met.

Description

Technical Field

[0001] The present invention relates to the field of bio-based new materials, and in particular to a distillation method for separating and purifying 1,3-propylene glycol based on renewable biomass fermentation. Background Art

[0002] 1,3-Propanediol (1,3-propanediol, 1,3-PDO) is a colorless, odorless, salty, hygroscopic viscous liquid. It is a raw material for the production of unsaturated polyesters, plasticizers, surfactants, emulsifiers and demulsifiers. In the polyurethane industry, it is often used as a raw material for polyester polyols, a starter for polyether polyols and a chain extender for polyurethanes. In the organic chemical industry, it is also an important monomer and intermediate. Its main use is as a polymer monomer, such as the synthesis of polytrimethylene terephthalate (PTT).

[0003] There are two methods for producing 1,3-propylene glycol: chemical method and biological fermentation method. The chemical method uses petroleum cracking products as raw materials and catalytically hydrogenates them under high temperature and high pressure. This method has complex production processes, harsh reaction conditions, and high requirements for equipment. The biological fermentation method uses renewable biomass as raw materials to produce 1,3-propylene glycol at room temperature and pressure. The biological fermentation method overcomes the limitations of traditional chemical industry conditions, and the raw materials are widely available and renewable, meeting the requirements of green chemical production.

[0004] The existing desalination methods of PDO fermentation broth mainly include: electrodialysis (Wang Xiaolin, Gong Yan, Tang Yu, etc. Electrodialysis for desalination of 1,3-propanediol fermentation broth [P]. Chinese patent: 031048714.2003-2-21), ion exchange (Wang Chonghui. Method for removing bacteria, protein and pigment from 1,3-propanediol fermentation broth [P]. Chinese patent: 200510047504.X.2005-10-19), nanofiltration desalination (Jin Ping, Wang Lingmin, Wang Chonghui, etc. Microbial fermentation production of 1,3- Method for extracting 1,3-propylene glycol from microbial fermentation broth [P]. Chinese Patent: 200710011414.4.2008-11-19.), alcohol precipitation method (Xiu Zhilong, Zhang Daijia, Gao Sujun, etc. Method for extracting and separating 1,3-propylene glycol from microbial fermentation broth [P]. Chinese Patent: 031335845.2003-6-2.), concentration crystallization method (Liu Dehua, Yang Dehua, Hao Jian, etc. An extraction process for producing 1,3-propylene glycol by fermentation [P]. Chinese Patent: 2007100655588.2007-4-16.), etc.

[0005] The ion exchange desalination method has a high desalination rate, but it has the disadvantages of frequent resin regeneration and large amounts of acid and alkali waste liquid for desalination of PDO fermentation broth, making it difficult to achieve industrial scale-up. Nanofiltration desalination is usually used in the pretreatment process of protein concentration and reverse osmosis. The removal rate of monovalent salts in PDO fermentation broth is extremely low and cannot meet the requirements of the PDO fermentation broth desalination process. The alcohol precipitation method for desalination of PDO fermentation broth also has the disadvantages of low desalination rate, large ethanol consumption, and high energy consumption.

[0006] At present, in the process of producing 1,3-propylene glycol by fermentation, electrodialysis is often used for desalination, but the electrodialysis desalination rate cannot reach 100%, so crude distillation is usually used to further remove the heavy components, otherwise the salt in the heavy components will easily clog the distillation reboiler, and the crude distillation fraction (i.e., the light component) is subjected to multi-tower continuous distillation to separate water, 2,3-butylene glycol and 1,3-propylene glycol. However, this process is long, the equipment investment is large, and the energy consumption is high.

[0007] Therefore, the distillation method for separation and purification of 1,3-propylene glycol based on renewable biomass fermentation needs further study. Summary of the invention

[0008] In view of the problems existing in the prior art, the present invention provides a distillation method for separating and purifying 1,3-propylene glycol based on renewable biomass fermentation. The distillation method adopts a crude distillation tower to distill the concentrated liquid obtained by multi-effect evaporation, and innovatively uses a scraper evaporator as a reboiler of the crude distillation tower, which can effectively avoid the clogging of the crude distillation tower reboiler by high-viscosity salt-containing materials. The combination of the crude distillation tower and the scraper evaporator achieves the separation and purification effects of the two processes of crude distillation and distillation in one process, simplifies the process flow, reduces equipment investment, and reduces energy consumption; moreover, the distillation method adopts a second distillation tower to achieve the simultaneous separation of 2,3-butanediol and 1,3-propylene glycol, simplifies the process, reduces energy consumption, and can prepare 1,3-propylene glycol with a purity greater than or equal to 99.9wt%, which fully meets the quality requirements of polymerization-grade products.

[0009] To achieve this object, the present invention adopts the following technical solutions:

[0010] The object of the present invention is to provide a distillation method for separating and purifying 1,3-propylene glycol based on renewable biomass fermentation, the distillation method comprising the following steps:

[0011] (1) fermenting renewable biomass to obtain 1,3-propanediol fermentation broth;

[0012] (2) subjecting the 1,3-propanediol fermentation broth of step (1) to ultrafiltration, electrodialysis, and multiple-effect evaporation in sequence to obtain a concentrated solution;

[0013] (3) distilling the concentrated liquid in step (2) using a crude distillation tower, wherein the crude distillation tower uses a scraper evaporator as a reboiler to obtain a distillate;

[0014] (4) dehydrating the distillate in step (3) using a first distillation tower to obtain a dehydrated liquid;

[0015] (5) using a second distillation tower to distill and separate the dehydrated liquid in step (4), extracting 2,3-butanediol from the top of the tower, extracting 1,3-propylene glycol crude liquid from the side line, and extracting heavy components from the bottom of the tower;

[0016] (6) Decolorizing the crude 1,3-propylene glycol solution of step (5) to obtain a 1,3-propylene glycol product solution.

[0017] The distillation method of the present invention uses renewable biomass as raw material, produces 1,3-propylene glycol through fermentation, obtains 1,3-propylene glycol fermentation liquid, and then sequentially performs ultrafiltration for sterilization and protein removal, electrodialysis for desalination, and multi-effect evaporation for removing part of water to obtain a concentrated solution, and then uses a crude distillation tower to distill the concentrated solution to obtain a distillate. The crude distillation tower is composed of a distillation tower and a scraper evaporator. The scraper evaporator is used as a reboiler of the distillation tower, which can effectively avoid the situation where high-viscosity salt-containing materials block the reboiler. Then, a first distillation tower is used to dehydrate the distillate, and a second distillation tower is used to achieve simultaneous separation of 2,3-butanediol and 1,3-propylene glycol, thereby simplifying the process and reducing energy consumption. 1,3-propylene glycol with a purity greater than or equal to 99.9wt% can be prepared, which fully meets the quality requirements of polymerization-grade products.

[0018] As a preferred technical solution of the present invention, in step (1), the fermentation is carried out using Klebsiella.

[0019] At present, there are two methods for producing 1,3-propylene glycol: chemical method (traditional chemical industry) and biological fermentation method (biorefining). The chemical method has a complex production process, harsh process conditions, cumbersome operation, high requirements for equipment and high costs, and it has always been difficult to achieve industrial-scale production. The biological fermentation method uses microorganisms as production tools and renewable biomass as raw materials to produce 1,3-propylene glycol in a fermentation tank; commonly used bacteria include Enterobacter, Klebsiella, Bacillus, Paenibacillus, Serratia, etc. Different strains differ in various factors in the fermentation synthesis of 1,3-propylene glycol. Among them, Klebsiella is considered to have the greatest industrial application prospects because its culture conditions are relatively simple and its fermentation substrate spectrum is wide. However, the biggest problem is that the components of the fermentation broth are complex and the product separation and purification are difficult. The traditional separation method uses multi-tower continuous distillation to separate and produce high-purity 1,3-propylene glycol products, but the investment in the distillation tower is relatively large.

[0020] As a preferred technical solution of the present invention, in step (2), the ultrafiltration is carried out using a ceramic membrane, and the filtration pore size of the ceramic membrane is 5-50nm, for example, 5nm, 7nm, 10nm, 12nm, 15nm, 17nm, 20nm, 25nm, 30nm, 35nm, 40nm, 45nm or 50nm, etc.

[0021] As a preferred technical solution of the present invention, in step (2), the ion exchange membrane used in the electrodialysis is a heterogeneous membrane or a semi-homogeneous membrane, and the conductivity of the desalted solution obtained by the electrodialysis is below 2000 μs / cm. More preferably, the ion exchange membrane used in the electrodialysis is a heterogeneous membrane, and the conductivity of the desalted solution obtained by the electrodialysis is below 1500 μs / cm.

[0022] As a preferred technical solution of the present invention, in step (2), the multi-effect evaporation is carried out by a multi-effect evaporator; the multi-effect evaporator includes any one of a triple-effect evaporator, a quadruple-effect evaporator, a fifth-effect evaporator, a sixth-effect evaporator or a seventh-effect evaporator, and the multi-effect evaporator is a reduced-pressure evaporation. More preferably, the multi-effect evaporation is carried out by a multi-effect evaporator, the multi-effect evaporator is a triple-effect evaporator or a quadruple-effect evaporator, and the operating pressure of the last-effect evaporator is -0.093 to -0.099 MPa.

[0023] As a preferred technical solution of the present invention, in step (2), the water content of the concentrated liquid is less than or equal to 40%.

[0024] As a preferred technical solution of the present invention, in step (3), the process parameters of the crude distillation tower include: a tower top operating pressure of 1-80 mmHg, such as 1 mmHg, 3 mmHg, 5 mmHg, 10 mmHg, 15 mmHg, 20 mmHg, 25 mmHg, 30 mmHg, 40 mmHg, 50 mmHg, 60 mmHg, 70 mmHg or 80 mmHg, etc.; more preferably, the tower top operating pressure of the crude distillation tower is 3-30 mmHg; and the PDO gasification rate is ≥99.5%.

[0025] As a preferred technical solution of the present invention, in step (4), the process parameters of the first distillation tower include: the tower top operating pressure is 40-200 mmHg; the water content of the dehydrated liquid is less than or equal to 0.5%.

[0026] In the present invention, the top operating pressure of the first distillation tower is 40-200 mmHg, for example, 40 mmHg, 60 mmHg, 70 mmHg, 80 mmHg, 90 mmHg, 100 mmHg, 120 mmHg, 150 mmHg, 180 mmHg or 200 mmHg.

[0027] As a preferred technical solution of the present invention, in step (5), the process parameters of the second distillation tower include: a theoretical plate number of 10-100, such as 10, 20, 30, 40, 50, 52, 55, 57, 60, 70, 80, 90 or 100, etc., the feed plate is located in the lower part of the tower, the side line extraction plate is located in the upper part of the tower, the top operating pressure is 1-90 mmHg, such as 1 mmHg, 5 mmHg, 7 mmHg, 10 mmHg, 12 mmHg, 15 mmHg, 20 mmHg, 40 mmHg, 60 mmHg, 70 mmHg or 90 mmHg, etc., and the reflux ratio is 0.5-10, such as 0.5, 1, 2, 3, 4, 5, 5.2, 5.5, 5.7, 6, 7, 8, 9 or 10, etc. More preferably, the process parameters of the second distillation tower include: the number of theoretical plates is 50-60, the top operating pressure is 5-15 mmHg, and the reflux ratio is 5-6.

[0028] As a preferred technical solution of the present invention, in step (6), the decolorization includes decolorization by activated carbon adsorption to obtain a colorless and odorless 1,3-propylene glycol product liquid.

[0029] Compared with the prior art solutions, the present invention has at least the following beneficial effects:

[0030] (1) The inventors have found that the traditional 1,3-propylene glycol concentrate has a complex composition. It is necessary to first use crude distillation to remove high-viscosity heavy components such as salt and protein, and then use a multi-tower continuous distillation method to separate and purify. The process flow is long and the investment is large. In this regard, the present invention provides a new distillation method, which uses a crude distillation tower to distill the concentrate obtained by multi-effect evaporation, and innovatively uses a scraper evaporator as a reboiler of the crude distillation tower, which can effectively prevent high-viscosity salt-containing materials from clogging the crude distillation tower reboiler. The combination of the crude distillation tower and the scraper evaporator achieves the separation and purification effects of the two processes of crude distillation and rectification in one process, simplifies the process flow, reduces equipment investment, and reduces energy consumption;

[0031] (2) The distillation method of the present invention can achieve the simultaneous separation of 2,3-butanediol and 1,3-propylene glycol by using a second distillation tower, which simplifies the process and reduces energy consumption. 1,3-propylene glycol with a purity greater than or equal to 99.9wt% can be prepared, which fully meets the quality requirements of polymerization-grade products. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 Schematic diagram of the process flow of the distillation method described in Example 1 of the present invention;

[0033] Figure 2 yes Figure 1 Schematic diagram of the structure after the medium crude distillation tower and the scraped surface evaporator are combined;

[0034] In the figure: 1. fermentation tank; 2. 1,3-propylene glycol fermentation broth; 3. ultrafiltration device; 4. ultrafiltration filtrate; 5. electrodialysis device; 6. electrodialysis desalting liquid; 7. multi-effect evaporator; 8. concentrate; 9. crude distillation tower; 10. crude distillate; 11. first distillation tower; 12. water; 13. dehydrated liquid; 14. second distillation tower; 15. 2,3-butanediol; 16. 1,3-propylene glycol crude liquid; 17. decolorization tower; 18. 1,3-propylene glycol product liquid; 19. scraper evaporator feed; 20. scraper evaporator; 21. crude distillate heavy components; 22. scraper; 23. scraper steam gas phase. DETAILED DESCRIPTION

[0035] The technical solution of the present invention is further described below with reference to the accompanying drawings and through specific implementation methods.

[0036] To better illustrate the present invention and facilitate understanding of the technical solution of the present invention, typical but non-limiting embodiments of the present invention are as follows:

[0037] Example 1

[0038] This embodiment provides a distillation method for separating and purifying 1,3-propylene glycol based on renewable biomass fermentation. Figure 1The process flow diagram of the distillation method described in this embodiment is shown, and the distillation method comprises the following steps:

[0039] (1) using renewable biomass (specifically glycerol) as a raw material, using Klebsiella to ferment and produce 1,3-propanediol to obtain 1,3-propanediol fermentation liquid 2;

[0040] The specific implementation method is as follows: after the fermentation tank 1 is inoculated, the fermentation liquid temperature is controlled at 37°C, the pH value is 6.5, the ventilation volume is 0.15vvm, and the stirring rate is 60rpm. During the fermentation process, the substrate glycerol concentration in the fermentation liquid is measured, and glycerol is added according to the glycerol consumption rate to ensure that the glycerol concentration in the fermentation liquid is 30g / L. The fermentation is carried out for 48 hours;

[0041] (2) subjecting the 1,3-propanediol fermentation broth 2 of step (1) to ultrafiltration, electrodialysis, and multiple-effect evaporation in sequence to obtain a concentrated solution, wherein the water content of the concentrated solution is less than or equal to 40%;

[0042] Ultrafiltration for removing bacteria and proteins is carried out in an ultrafiltration device 3 to obtain an ultrafiltration filtrate 4, wherein the ultrafiltration is carried out using a ceramic membrane with a filtration pore size of 50 nm;

[0043] The electrodialysis for desalination is carried out in the electrodialysis device 5 to obtain the electrodialysis desalted liquid 6. The process parameters of the electrodialysis are as follows: the ion exchange membrane used is a heterogeneous membrane, and the conductivity of the desalted liquid is reduced to 1500 μs / cm after the electrodialysis desalination;

[0044] The multi-effect evaporation is used to remove part of the water to obtain a concentrated solution 8; the multi-effect evaporation is carried out by a multi-effect evaporator 7, and the process parameters of the multi-effect evaporator 7 are: a four-effect evaporator, and the operating pressure of the last effect evaporator is -0.096MPa;

[0045] (3) using a crude distillation tower 9 to distill the concentrated liquid 8 of step (2); Figure 2 The schematic diagram of the structure after the crude distillation tower and the scraper evaporator are combined is shown. The crude distillation tower 9 uses the scraper evaporator 20 as a reboiler. After the concentrated liquid 8 enters the crude distillation tower 9, the crude distillate 10 is obtained at the top of the tower. The bottom liquid enters the scraper evaporator 20 as the scraper evaporator feed 19 and is distilled under the action of the scraper 22. The crude distillate heavy component 21 is obtained at the bottom of the scraper evaporator 20, and the scraper steam gas phase 23 is obtained at the top of the scraper evaporator 20, and all of them are returned to the crude distillation tower 9; wherein, the tower top operating pressure of the crude distillation tower 9 is 20 mmHg, the PDO gasification rate is ≥99.5%, and the crude distillate 10 is obtained;

[0046] (4) using a first distillation tower 11 to dehydrate the crude distillate 10 of step (3), controlling the top operating pressure of the first distillation tower to be 80 mmHg, obtaining water 12 at the top of the tower, and obtaining a dehydrated liquid 13 having a water content of less than or equal to 0.5% at the bottom of the tower;

[0047] (5) using a second distillation tower 14 to distill and separate the dehydrated liquid 13 of step (4), the theoretical number of plates is 55, the feed plate is located in the lower part of the tower, the side line extraction plate is located in the upper part of the tower, the tower top operating pressure is 10 mmHg, and the reflux ratio is 5; 2,3-butanediol 15 is extracted from the top of the tower, 1,3-propylene glycol crude liquid 16 with a purity greater than or equal to 99.9 wt% is extracted from the side line, and heavy components such as glycerol are extracted from the bottom of the tower;

[0048] (6) The crude 1,3-propylene glycol liquid 16 of step (5) is decolorized by activated carbon adsorption in a decolorization tower 17 to obtain a colorless and odorless 1,3-propylene glycol product liquid 18.

[0049] The materials at each stage in this embodiment were tested by gas chromatography or liquid chromatography, and the test results are summarized in Table 1.

[0050] Table 1

[0051]

[0052] Note: “ / ” in the table means not tested.

[0053] It can be seen from Table 1 that in the 1,3-propylene glycol product liquid prepared in this embodiment, the purity of 1,3-propylene glycol is 99.92 wt % and the chromaticity is 5 dark blue. During the distillation process, the loss of 1,3-propylene glycol product is 0.2%.

[0054] Example 2

[0055] This embodiment provides a distillation method for separating and purifying 1,3-propylene glycol based on renewable biomass fermentation, and the distillation method comprises the following steps:

[0056] (1) using renewable biomass (specifically glycerol) as a raw material, using Klebsiella to ferment and produce 1,3-propanediol to obtain a 1,3-propanediol fermentation broth;

[0057] The specific implementation method is as follows: after the fermentation tank is inoculated, the fermentation liquid temperature is controlled at 37°C, the pH value is 6.5, the ventilation volume is 0.15vvm, and the stirring rate is 60rpm. During the fermentation process, the substrate glycerol concentration in the fermentation liquid is measured, and glycerol is added according to the glycerol consumption rate to ensure that the glycerol concentration in the fermentation liquid is 30g / L. The fermentation is carried out for 48 hours;

[0058] (2) subjecting the 1,3-propanediol fermentation broth of step (1) to ultrafiltration, electrodialysis, and multiple-effect evaporation in sequence to obtain a concentrated solution, wherein the water content of the concentrated solution is less than or equal to 40%;

[0059] Ultrafiltration for removing bacteria and proteins to obtain ultrafiltration filtrate, wherein the ultrafiltration is performed using a ceramic membrane with a filtration pore size of 50 nm;

[0060] Electrodialysis for desalination to obtain an electrodialysis desalted liquid, wherein the process parameters of the electrodialysis are as follows: the ion exchange membrane used is a heterogeneous membrane, and the conductivity of the desalted liquid after electrodialysis desalination is reduced to 1500 μs / cm;

[0061] Multi-effect evaporation is used to remove part of the water to obtain a concentrated solution; the multi-effect evaporation is carried out using a multi-effect evaporator, and the process parameters of the multi-effect evaporator are: a four-effect evaporator, and the operating pressure of the last-effect evaporator is -0.096MPa;

[0062] (3) distilling the concentrated liquid of step (2) using a crude distillation tower, wherein the crude distillation tower uses a scraper evaporator as a reboiler, the top operating pressure of the crude distillation tower is 20 mmHg, and the PDO gasification rate is ≥99.5%, to obtain a distillate;

[0063] (4) using a first distillation tower to dehydrate the distillate of step (3), controlling the top operating pressure of the first distillation tower to be 80 mmHg, and obtaining a dehydrated liquid having a water content of less than or equal to 0.5%;

[0064] (5) using a second distillation tower to distill and separate the dehydrated liquid in step (4), the theoretical number of plates being 55, the feed plate being located in the lower part of the tower, the side line extraction plate being located in the upper part of the tower, the tower top operating pressure being 10 mmHg, and the reflux ratio being 6; extracting 2,3-butanediol from the tower top, extracting a crude 1,3-propylene glycol liquid having a purity of greater than or equal to 99.9 wt % from the side line, and extracting heavy components such as glycerol from the tower bottom;

[0065] (6) The crude 1,3-propylene glycol liquid of step (5) is subjected to activated carbon adsorption decolorization in a decolorization tower to obtain a colorless and odorless 1,3-propylene glycol product liquid.

[0066] The materials at each stage in this embodiment were tested by gas chromatography or liquid chromatography, and the test results are summarized in Table 2.

[0067] Table 2

[0068]

[0069] Note: “ / ” in the table means not tested.

[0070] It can be seen from Table 2 that in the 1,3-propylene glycol product liquid prepared in this embodiment, the purity of 1,3-propylene glycol is 99.96 wt % and the chromaticity is 5 dark blue. During the distillation process, the loss of 1,3-propylene glycol product is 0.2%.

[0071] Comparative Example 1

[0072] This comparative example provides a distillation method for separating and purifying 1,3-propylene glycol based on renewable biomass fermentation. Compared with Example 1, the only difference is that in step (3), a crude distillation tower is used to distill the concentrated liquid, and the reboiler of the crude distillation tower is a conventional heat exchanger, and the obtained distillate directly enters the first distillation tower for dehydration.

[0073] The materials at each stage in this comparative example were tested by gas chromatography or liquid chromatography, and the test results are summarized in Table 3.

[0074] Table 3

[0075]

[0076] Note: “ / ” in the table means not tested.

[0077] As can be seen from Table 3, in the 1,3-propylene glycol product liquid prepared in this comparative example, the purity of 1,3-propylene glycol is 99.95wt% and the chromaticity is 5 dark blue. The product quality is qualified, but the loss of the product in the crude distillation process is large. The crude distillation tower using a conventional reboiler has too high a concentration of 1,3-propylene glycol product remaining in the bottom of the kettle, and the loss of 1,3-propylene glycol in the distillation process is 8%.

[0078] Comparative Example 2

[0079] This comparative example provides a distillation method for separating and purifying 1,3-propylene glycol based on renewable biomass fermentation. Compared with Example 1, the only difference is that in step (3), a crude distillation tower is used to distill the concentrate, and the reboiler of the crude distillation tower is a conventional heat exchanger. The obtained crude distillation bottoms enter the scraped evaporator for further distillation and recovery of 1,3-propylene glycol and other products.

[0080] The materials at each stage in this comparative example were tested by gas chromatography or liquid chromatography, and the test results are summarized in Table 4.

[0081] Table 4

[0082]

[0083] Note: “ / ” in the table means not tested.

[0084] It can be seen from Table 4 that in the 1,3-propylene glycol product liquid prepared in this comparative example, the purity of 1,3-propylene glycol is 99.95wt% and the chromaticity is 5 dark blue. The product quality is qualified, but the crude still bottom needs to be distilled twice (scraper evaporation) to recover the 1,3-propylene glycol therein. The two distillations prolong the heating time of the material, increase the viscosity of the material, and reduce the yield of 1,3-propylene glycol. The total yield of the two distillation processes is 98.8%.

[0085] In summary, the present invention provides a distillation method for separating and purifying 1,3-propylene glycol based on renewable biomass fermentation. The distillation method adopts a crude distillation tower to distill the concentrated liquid obtained by multi-effect evaporation, and innovatively uses a scraper evaporator as a reboiler of the crude distillation tower, which can effectively avoid the high-viscosity salt-containing materials from clogging the crude distillation tower reboiler. The combination of the crude distillation tower and the scraper evaporator achieves the separation and purification effects of the crude distillation and distillation processes in one process, simplifies the process flow, reduces equipment investment, and reduces energy consumption; moreover, the distillation method adopts a second distillation tower to achieve the simultaneous separation of 2,3-butanediol and 1,3-propylene glycol, simplifies the process, reduces energy consumption, and can prepare 1,3-propylene glycol with a purity greater than or equal to 99.9wt%, which fully meets the quality requirements of polymerization-grade products.

[0086] The present invention illustrates the detailed structural features of the present invention through the above embodiments, but the present invention is not limited to the above detailed structural features, that is, it does not mean that the present invention must rely on the above detailed structural features to be implemented. Those skilled in the art should understand that any improvement of the present invention, equivalent replacement of the components selected by the present invention, addition of auxiliary components, selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

[0087] The preferred embodiments of the present invention are described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the technical concept of the present invention, a variety of simple modifications can be made to the technical solution of the present invention, and these simple modifications all belong to the protection scope of the present invention.

[0088] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not further describe various possible combinations.

[0089] In addition, various embodiments of the present invention may be arbitrarily combined, and as long as they do not violate the concept of the present invention, they should also be regarded as the contents disclosed by the present invention.

Claims

1. A distillation method for separating and purifying 1,3-propylene glycol based on renewable biomass fermentation, characterized in that: The distillation method comprises the following steps: (1) fermenting renewable biomass to obtain 1,3-propanediol fermentation broth; (2) subjecting the 1,3-propanediol fermentation broth of step (1) to ultrafiltration, electrodialysis, and multiple-effect evaporation in sequence to obtain a concentrated solution; (3) distilling the concentrated liquid in step (2) using a crude distillation tower, wherein the crude distillation tower uses a scraper evaporator as a reboiler to obtain a distillate; (4) dehydrating the distillate in step (3) using a first distillation tower to obtain a dehydrated liquid; (5) using a second distillation tower to distill and separate the dehydrated liquid in step (4), extracting 2,3-butanediol from the top of the tower, extracting 1,3-propylene glycol crude liquid from the side line, and extracting heavy components from the bottom of the tower; (6) Decolorizing the crude 1,3-propylene glycol solution of step (5) to obtain a 1,3-propylene glycol product solution.

2. The distillation method according to claim 1, characterized in that: In step (1), the fermentation is carried out using Klebsiella.

3. The distillation method according to claim 1 or 2, characterized in that: In step (2), the ultrafiltration is performed using a ceramic membrane, and the filtration pore size of the ceramic membrane is 5-50 nm.

4. The distillation method according to any one of claims 1 to 3, characterized in that: In step (2), the ion exchange membrane used in the electrodialysis is a heterogeneous membrane or a semi-homogeneous membrane, and the conductivity of the desalted liquid obtained by the electrodialysis is below 2000 μs / cm.

5. The distillation method according to any one of claims 1 to 4, characterized in that: In step (2), the multiple-effect evaporation is performed using a multiple-effect evaporator; the multiple-effect evaporator includes any one of a triple-effect evaporator, a quadruple-effect evaporator, a fifth-effect evaporator, a sixth-effect evaporator or a seventh-effect evaporator, and the multiple-effect evaporator is a reduced-pressure evaporation.

6. The distillation method according to any one of claims 1 to 5, characterized in that: In step (2), the water content of the concentrated solution is less than or equal to 40%.

7. The distillation method according to any one of claims 1 to 6, characterized in that: In step (3), the process parameters of the crude distillation tower include: a tower top operating pressure of 1-80 mmHg, and a PDO gasification rate of ≥99.5%.

8. The distillation method according to any one of claims 1 to 7, characterized in that: In step (4), the process parameters of the first distillation tower include: the tower top operating pressure is 40-200 mmHg; the water content of the dehydrated liquid is less than or equal to 0.5%.

9. The distillation method according to any one of claims 1 to 8, characterized in that: In step (5), the process parameters of the second distillation tower include: the number of theoretical plates is 10-100, the feed plate is located in the lower part of the tower, the side line extraction plate is located in the upper part of the tower, the top operating pressure is 1-90 mmHg, and the reflux ratio is 0.5-10.

10. The distillation method according to any one of claims 1 to 9, characterized in that: In step (6), the decolorization includes decolorization by activated carbon adsorption to obtain a colorless and odorless 1,3-propylene glycol product liquid.

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